This invention relates to surveillance of telephone calls over a public communications link and is particularly concerned with providing assistance for such surveillance to law enforcement agencies. It particularly concerns surveillance of voice over IP (i.e., cable) networks.
Requirements for enabling surveillance of electronic communications have been enacted into public law (e.g., Public Law 103-414 enacted Oct. 25, 1994; CALEA Communications Assistance for Law Enforcement Act) reciting requirements for assuring law enforcement access to electronic communications. Such access is required to be in real time, have full time monitoring capabilities, simultaneous intercepts, and feature service descriptions. The requirements specifically include capacity requirements and function capability. It is incumbent upon communication carriers to provide such capability and capacity.
While initially limited in scope, at present, to certain communications technology it is almost assured that it will be extended to new forms of communication. New technologies require extension of CALEA to the new phone system technologies. With the advent of IP telephony it is desirable to provide surveillance capabilities for application to IP telephony.
One of the impediments to surveillance is the necessity of having dedicated equipment to perform the monitoring function. It would be useful to perform such surveillance of a targeted phone with non-dedicated telephone equipment. With use of such non-dedicated equipment it is desirable to distinguish normal calls from surveillance calls.
Surveillance of IP telephony may be performed through the use of conventional telephone equipment, according to principles of the invention while preventing giving indication to the monitored phone of the monitoring activity. The user of the monitoring phone is alerted to such surveillance use prior to pick up, by an agent for engagement of the monitoring phone, in response to the alert. Such alerts may assume many forms such as ringing, visual indicators, data readouts, activating ancillary equipment, various flags, etc. This alert prior to surveillance is distinct from alerts used for normal non-surveillance calls, which the monitoring phone is capable of receiving.
In an IP telephone environment, a cable modem bank (CMB) or an IP Phone intercept List (IP-PIL) lists the IP phones to be monitored and responds when one of those listed phones to be monitored becomes active. In response to notification by an IP Address Mapping Check Point with the IP-PIL, a distinctive alert is delivered to the monitoring phone, which indicates the call""s existence and the monitoring purpose to be performed. The IP Address Mapping Check Point and associated WatchDog program alerts the monitoring phone when the monitored phone is in the process of receiving a call. In both instances the monitoring phone is controlled not to be active until both parties of the monitored call are connected and active.